Selected components in a typical prior art magnetic storage device (disk drive) 10 are illustrated in FIG. 1 in simplified block form. Although only one disk 16 and one slider 11 are shown, there may be multiple disks in a drive and typically there are two sliders per disk, i.e., one for each surface of the disk. This disk drive comprises a thin film magnetic disk 16 for recording data, a slider or magnetic head 11 that carries out the reading and writing of data in tracks on the magnetic disk 16. The disk is attached to spindle 18 which is rotated by spindle motor 14. The slider includes a read head 12 and a write head 19 which are attached to suspension 13. The disk 16 includes a plurality of thin films 17 in which magnetic transitions are recorded. Sliders are fabricated in sets on a wafer using semiconductor-type processing methods. Typically the read head is formed first, but the write head can also be fabricated first. The conventional write head is inductive. The layers and structures in the sliders are first deposited on the wafer, then the wafer is sliced into rows or individual sliders to expose the transducer elements. The cut surfaces of the sliders are typically lapped and a protective overcoat is deposited on the air-bearing surface. Typically, a slider is formed with an aerodynamic pattern of protrusions (air-bearing features) on the air-bearing surface (ABS) which enable the slider to fly at a constant height close to the disk during operation of the disk drive. The recording density of a magnetic disk drive is limited by the distance between the read and write heads and the magnetic media. Smaller spacing or “fly height” is desired to increase the recording density. The magnetic domains in the media on can be written longitudinally or perpendicularly.
In a disk drive using perpendicular recording, the recording head is designed to direct magnetic flux through the recording layer in a direction which is generally perpendicular to the plane of the disk. Typically the disk for perpendicular recording has a hard magnetic recording layer and a magnetically soft underlayer. During recording operations using a single-pole type head, magnetic flux is directed from the main pole of the recording head perpendicularly through the hard magnetic recording layer, then into the plane of the soft underlayer and back to the return pole in the recording head.
In U.S. Pat. No. 6,584,676 to Chang, et al., Jul. 1, 2003, a method is described for finishing a trimmed pole tip read/write head that includes a substrate with a pole tip structure having a shield, a shield/pole, and an outer pole. A gap region separates the pole and the shield/pole. First, pole tip trimming is performed to the read/write head to remove matter from the shield/pole, the pole, and the gap region. This defines a bridge composed of inward-facing extensions of the pole and shield/pole interconnected by an intervening region. This bridge separates recessed “trenches,” each formed by removing a contiguous mass from the shield/pole, the gap region, and the pole. Next, an overlayer is applied over the pole tip structure, filling the recessed trenches. The coated structure is then trimmed to remove all coating material overlying the shield/pole and pole. Trimming is continued to additionally remove a top layer of the protrusions of the pole and shield/pole to remove any rounded edges created by pole tip patterning, resulting in a more distinct write head. The refilled trenches of the recessed areas impart improved resistance to corrosive attack, to head-crashes from the release of accumulated debris, and to mechanical damage of the trimmed pole-tip structure.
In published U.S. patent application 20050073775 by Chang, et al., Apr. 7, 2005 a process of milling pole tip in a write head for longitudinal recording is described. As a first step a thin film protective layer is deposited upon the pole tip on the ABS surface. Following the deposition of the protective layer 100, the FIB tool is utilized to mill the areas within the milling boxes as was done in the prior art. The improvement that results from the protective layer of the invention is a reduction in the rounding of the edges. Following the FIB milling step, the protective layer is removed from the head by such means as a chemical etch, burnishing or other generally known methods.
Ferrofluids are liquids with ferromagnetic particles suspended in them. One use of ferrofluids is to visualize the recorded pattern on magnetic disks or for magnetic flaw detection. U.S. Pat. No. 4,946,613 to Ishikawa Aug. 7, 1990 describes photosetting ferrofluid compositions that include photosetting resin. In one embodiment the carrier itself includes a photosetting resin. When the photosetting ferrofluid is used for magnetic flaw detection or to visualize a magnetically recorded pattern, the ferrofluid is first applied onto the surface of the article on which a magnetic field has been formed. The ferrofluid is then urged to swell by being attracted either by the leaked magnetic flux caused by the defective region or by the variation in the magnetic flux of the recorded magnetic signal. This forms a pattern of the ferrofluid corresponding to the pattern of the magnetic flux. Next the article is exposed to a beam of light having a specific wave length sufficient to set or harden the photosetting resin fixing the pattern of the ferrofluid formed by the magnetic flux. Where sharp photographic images must be obtained, the ferrofluid uses a carrier of low viscosity. By virtue of the use of a low viscosity carrier, the ferrofluid swells up with steep inclinations. Subsequently, a light beam of a specific wave length sufficient for setting the photosetting resin added in the ferrofluid as a pattern fixing agent is directed to the fluid so as to fix the pattern formed by the ferrofluid.
The use of ferrofluids have also been described in connection with the creation of self-aligning masks for optical masking and chemical masking. Yellen, et al. described the use of nanometer sized ferrofluids with alignment marks on a substrate and an applied external field. (“Programmable Self-Aligning Ferrofluid Masks for Lithographic Applications”, IEEE Transactions On Magnetics, vol. 40, no. 4 July 2004.) When the external field is applied normal to the plane of the substrate the ferrofluid particles are preferentially deposited over one of the poles of ferromagnetic islands which are used as the alignment marks.